We discuss the present status of auantum electrodynamics (QED) investigations of electron correlations in second order in α for heavy fewelectron atoms. A complete evaluation of all two-electron QED contributions of order α² is presented for the 2p_½-2s transition in high-Z Li-like ions. In particular, the two-photon exchange correction beyond the Breit approximation is calculated for highly charged ions with Z < 50. The total theoretical value of 280.44(9)(20) eV is found for the 2p_½-2s transition energy in Li-like U.